A constant velocity universal joint is roughly classified into a fixed-type constant velocity universal joint and a slide-type constant velocity universal joint. The fixed-type constant velocity universal joint allows only angular displacement and is mainly used on the wheel side of an automotive drive shaft, for example. On the other hand, the slide-type constant velocity universal joint allows angular displacement and axial displacement (plunging) and is mainly used on the differential gear side of an automotive drive shaft.
This kind of constant velocity universal joint is provided with a boot for preventing lubricating components sealed inside the joint from leaking to the outside and preventing foreign matter from intruding from the outside.
As an example of a constant velocity universal joint provided with this kind of boot, a Rzeppa-type constant velocity universal joint which is one of a fixed-type constant velocity universal joint is illustrated in FIG. 20.
This constant velocity universal joint 201 includes an outer race 202, an inner race 203, balls 204 and a cage 205 as main components, and an internal component set 206 including the inner race 203, the balls 204 and the cage 205 is accommodated and disposed inside the outer race 202.
The outer race 202 has an opening at one end thereof, and a plurality of curved track grooves 207 are formed on inner spherical surface thereof. A plurality of curved track grooves 208 are formed on the outer spherical surface of the inner race 203, and a shaft 209 is spline-fitted in the center hole 219 thereof and is prevented from coming off by means of a circlip 210. The plurality of balls 204 are disposed between the track grooves 207 of the outer race 202 and the track grooves 208 of the inner race 203, and the balls 204 are retained in the pockets 217 of the cage 205 disposed between the outer race 202 and the inner race 203.
The opening of the outer race 202 is covered with a boot 211. This boot 211 has a large-diameter end section 212, a small-diameter end section 213 and a bellows section 214 connecting the large-diameter end section 212 and the small-diameter end section 213. The large-diameter end section 212 is installed on the outer peripheral surface 220 of the opening end section 218 of the outer race 202, the small-diameter end section 213 is installed on the outer peripheral surface 221 of the shaft 209, and the respective installation portions are fixed by tightening boot bands (215 and 216).
As the structure of the installation portions of the opening end section 218 of the outer race 202 and the large-diameter end section 212 of the boot 211 or the structure of the installation portions of the shaft 209 and the small-diameter end section 213, various structures are known. Examples of the structures are illustrated in FIG. 21 and FIGS. 22A to 22C. The same portions as those illustrated in FIG. 20 and the portions having the same functions as those of the portions illustrated therein are described with the same reference numerals.
FIG. 21 illustrates an example of the structure of the installation portions of the large-diameter end section 212 of the boot 211 and the outer peripheral surface 220 of the opening end section 218 of the outer race 202. A fitting groove 225 is formed on the outer peripheral surface 220 of the opening end section 218 of the outer race 202, and a protruding section 226 is provided annularly on the inner peripheral surface 224 of the large-diameter end section 212. The large-diameter end section 212 is installed on and fixed to the opening end section 218 of the outer race 202 by fitting this protruding section 226 into the fitting groove 225 and by tightening the boot band 215 on the outer peripheral surface of the large-diameter end section 212.
With this structure, the sealability of the large-diameter end section 212 of the boot 211 is ensured. Further, since the protruding section 226 is fitted into the fitting groove 225, when the large-diameter end section 212 is installed on the opening end section 218 of the outer race 202, the positioning thereof in the axial direction is made possible. The structure of the installation portions of the large-diameter end section 212 and the opening end section 218 of the outer race 202 is also applied to the structure of the installation portions of the small-diameter end section 213 of the boot 211 and the shaft 209 illustrated in FIG. 20.
In the outer peripheral surface 220 of the opening end section 218 of the outer race 202, a tapered surface 227 is formed at the portion on the side of the opening of the outer race from the fitting groove 225, and this tapered surface 227 and the fitting groove 225 form an acute angle section 223. This acute angle section 223 bites into the inner peripheral surface 224 of the large-diameter end section 212, thereby improving the sealability of the large-diameter end section 212 and preventing the large-diameter end section 212 from coming off from the opening end section 218 of the outer race 202 (refer to Patent Document 1).
FIGS. 22A to 22C illustrate the structure of the installation portions of the opening end section 218 of the outer race 202 and the large-diameter end section 212 of the boot 211 as in the case of FIG. 21. As illustrated in FIG. 22B, a fitting groove 241 is formed on the outer peripheral surface 220 of the opening end section 218 of the outer race 202, and on the outer peripheral surface 220 of the opening end section 218 of the outer race 202, an annular protruding section 239 is formed on the side of the opening of the outer race from the fitting groove 241. As illustrated in FIG. 22A, the large-diameter end section 212 of the boot 211 has a tapered section 237, a protrusion 240, a dent 238 and a shoulder contact section 236 on the inner peripheral surface 224 thereof. With this structure, when the large-diameter end section 212 of the boot 211 is installed on the opening end section 218 of the outer race 202, the protruding section 239 of the opening end section 218 of the outer race 202 is fitted into the dent 238 as illustrated in FIG. 22C, thereby preventing the large-diameter end section 212 from coming off from the opening end section 218 of the outer race 202, the protrusion 240 is brought into close contact with the fitting groove 241 of the opening end section 218 of the outer race 202, thereby imparting sealability to the large-diameter end section 212, and the opening end section 218 of the outer race 202 is brought into contact with the shoulder contact section 236, thereby facilitating the positioning of the large-diameter end section 212 in the axial direction. Even in this prior art, the boot band 215 is tightened on the outer peripheral surface of the large-diameter end section 212 as illustrated in FIG. 22C, whereby the large-diameter end section 212 is installed on and fixed to the opening end section 218 of the outer race 202 (refer to Patent Document 2).    [Patent Document 1] Japanese Patent Application Laid-open No. 2001-208215    [Patent Document 2] Japanese Patent Application Laid-open No. 2006-226453